B46 / B48 — 2.0L Inline-4 Turbo
Isle & Alpine · Engine Guide
B46 / B48 — 2.0L Inline-4 Turbo
The four-cylinder half of the modular family — B58 architecture, minus two cylinders.
Key Specifications
Displacement1,998 cc
ConfigurationInline-4 · twin-scroll turbo
Bore × Stroke82.0 × 94.6 mm
InjectionDirect, 200→350 bar (TU)
B46 Output248 hp (185 kW) @ 5,200–6,500
B46 Torque258 lb-ft (350 Nm) @ 1,450
B48TU Output302 hp (225 kW)
B48TU Torque332 lb-ft (450 Nm)
Fitted To
F30 330iG20 330iF22 230iG01 X3 30iF48 X1 28iF39 X2 28i
Oil Specification
Oil Spec
BMW Longlife-01 (petrol); LL-17 FE+ for TU variants.
What Makes It Special
Same modular family as the B58 — identical per-cylinder design. The B46 is the ULEV variant and the B48 the SULEV version; the TU (Technical Update) variants raise injection pressure from 200 bar to 350 bar for better combustion efficiency.
Unlike the inherently balanced inline-six, the four-cylinder adds a balance shaft for NVH refinement. The B46TU/B48TU also introduced modified pistons with higher compression.
Maintenance Watch Items
- Oil filter housing gasket is the most common leak point — replace proactively at major services.
- Timing chain tensioner — listen for rattle on cold start, particularly on pre-TU versions.
- Carbon buildup on intake valves (direct injection only) — walnut blast every 60–80k miles.
- Electric water pump — long life, but expensive to replace when it fails.